Overall Objectives: The objectives of these studies are to determine the effects of piperonyl butoxide, a widely used pesticidal synergist, on mouse liver microsomal enzyme induction. Since piperonyl butoxide acts by inhibition drug metabolism, we will also determine the involvement of drug metabolism in the induction process. Furthermore, we will determine the effects of piperonyl butoxide on the metabolism of several carcinogens. These effects will then be correlated with biological responses to hepatocarcinogens; e.g. DNA binding, liver cell necrosis and carcinogenesis. Goals Set for Current Year: In this year we set 2 goals. 1. Define the effects of PB on mixed function oxidase induction. 2. Quantitate the effects of PB on the metabolism of carcinogens. In order to accomplish these goals we set out to determine the effects of PB on the induction of many mixed function oxidases by 3- methylcholanthrene and phenobarbital in inbred and random bred mice. In the case of carcinogen metabolism, we set out to quantitate the effects of PB on dimethylnitrosamine, benzpyrene, and acetylaminofluorene metabolism. Each response was to be measured in vitro and in vivo if possible and some aspect of toxicity was to be determined.